Q: For PC used in ultra-low temperature environments (-30°C to -40°C), which impact modifier should be selected (e.g., silicone-based or MBS)?

If the application scenario only requires ultra-low temperature impact resistance (-30°C to -40°C), both silicone-based impact modifiers and MBS impact modifiers can perform well. Both demonstrate excellent impact efficiency at both ambient and low temperatures.

However, when the application demands both low-temperature impact resistance and long-term heat and humidity resistance, a significant performance gap emerges.

Outdoor applications (such as EV charging stations, 5G infrastructure enclosures, photovoltaic components, etc.) typically require validation through damp heat testing (85°C/85% RH, 21 days) or post-boiling impact testing to confirm long-term reliability. Under these conditions, silicone-based impact modifiers exhibit clear advantages – the silicone core in their core-shell structure contains no unsaturated double bonds, offering far superior heat and humidity aging resistance compared to the polybutadiene rubber phase in MBS modifiers. Comparative test data shows that at the same 5% loading level in a PC matrix, EVERSUN USI-3301 maintains an impact retention value of 734 J/m after 168 hours of 85°C/85% RH damp heat aging.

Selection recommendations for outdoor applications: silicone-based impact modifiers

USI-3301: Balances heat and humidity resistance, weatherability, and low-temperature impact performance (-30°C). Suitable for outdoor PC/PC-ABS applications requiring high comprehensive durability.

 USI-3304: Offers the best ultra-low temperature (-40°C) impact performance, ideal for scenarios demanding exceptional retention of low-temperature toughness

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